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Frontpanel Design (diy attempt)


tago
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Hi all,

before continuing my NG based synth controller and want to do a less complicated project to gain more expierence. I thought a SEQ V4 would be a good candidate.

I already started with the layout (a mix of Wilba's and latigid's layouts) and have some questions. I'd be very happy if i could get some help here. Like latigids design i want to layout two identical pcbs (8steps/columns per pcb) for each side.

Thanks in advance!

Edited by tago
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My first questions are LED related.

I want to use different colored 10mA leds with 6-8 mcd and wonder if this is going to be too dark (4x8 matrix).

Another point: What do you think of using 2 leds instead of one dual color led per step on the top row? (reason: dual color leds are harder to get and much brighter than standard leds / could look good on a frontpanel)

Edited by tago
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Peter, are you still planning on

On 25.11.2017 at 4:25 PM, Hawkeye said:

Here is a quad MB-LRE8x2, 1024 green LEDs (green = rather problematic, currently don't know the mcd rating though), 47R resistors, ULN drivers. Brightness is more than fine:

Just try it out with a test build!
Many greets,
Peter

 

 

Peter, are you still planning on making the MBProgramma a documented project for us mere assemblers? That thing looks like the master solution for every synth controller needs. imagine having that connected to the Seq and all those LED rings showing automations...

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Hi u-link,

Quote

Peter, are you still planning on making the MBProgramma a documented project for us mere assemblers?

yes, it is on the medium-term list, Andy has created nice PCBs with the exact same OLEDs, but with RGB-backlit encoders (which saves space in comparison to the LED rings, and also adds a bit of "improved readability" because of the option to have different colors for different sections of the controller).

But, currently the new MBSEQv4+ is in the central focus, so the availability and build-documentation of these boards comes first. But there is a good chance for MBProgramma availability (and documentation) somewhen in 2018 (rather later than sooner in the year, as it is a complex project).

Many greets,
Peter

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Just now, tago said:

I was planning to connect the LEDs directly to the shift registers like here: http://www.ucapps.de/midibox_seq/mbseq_v4_dio_wilba_layout.pdf

Will this work?

Yes, it will work technically, but you should test the brightness before committing to a special LED type/manufacturer. You can do this manually just by testing a bit on breadboard. LEDs may vary in brightness and i would not rely on mcd values stated by the manufacturers... Better to test early, than to be sorry later on :-).

For the Programma, I also tested the green MBLREs LEDs before soldering them in, with and without the ULNs (same as SEQ in this case). While it worked without ULNs, the brightness was visibly reduced without the ULNs, but only when all LEDs where "on" (maybe I hit a current limit somewhere). But: it depends on the number of LEDs you are driving, and especially on their type, so do test them and don't shy back from "low" current-limiting resistor values like 47R, even if they would produce high LED currents on paper... what counts in the end is the average current flowing. With only 1/8th (or 12.5%) on-cycle-time, that will be low anyways... so you should get low-current LEDs. Some people also successfully direct-drive matrix-connected LEDs, with low cycle times (0R current limiting).

Many greets and good luck!
Peter
 

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I unfortunately have only two LEDs per color laying around here, i'm not sure i can test this accurately with them. I encountered small brightness differences between the colors, as expected.

Wilba's panel doesn't use drivers http://www.midibox.org/dokuwiki/doku.php?id=wilba_mb_seq_construction_guide

Currently i have a 4x8 matrix per pcb for LEDs and the remaining 4 pins of the dout register for the button input matrix.

One thing i saw in http://www.ucapps.de/midibox_seq/mbseq_v4_dio_wilba_layout.pdf is double use of a dout register (M1-8) for LEDs and BTN matrices. Would it be possible to do the same (using only 4 outs of a 8 out register and get slower cycle time for more brightness? Or would this be 1/8th anyway?

 

 

Edited by tago
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I generally wonder why it's a 1/8th cycle in a 8x8 matrix for example. I'd think its 1/64th cycle.


Edit: ok, i read more about matrices and it seems that only one axis cycles and the other works simlutaneously. That would mean a 4x8 matrix could be twice as bright as a 8x8 matrix, right?

Edited by tago
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Yes, 25% duty cycle in a 4x8 matrix, but i think MIDIbox primarily supports 8x8 and these are fine generally, you can drive 64 LEDs with only 16 shift register outputs, which is very economic. It just needs bright LEDs, so better test them, than to believe in datasheets :-). Also, i might have an explanation about reduced brightness, when all LEDs are on: the shift registers generally only support 20mA output per pin, so these 20mA would be shared amongst 8 LEDs, if all are on. Totally ok for low-current LEDs, but it might be dim otherwise.

Many greets,
Peter

 

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Yes, with a bit of hacking you can do that easily, but the default for the SEQ is 8x8 for Wilba's variant. From a developer point of view, it makes only sense to support frontpanel variants that are built in larger quantities (like Wilba's panel and soon Andy's new panel).

But as the SEQ is fully open source you are totally free to modify it to your heart's desire, you just have to keep maintaining it, when new versions are released.

If you ask for my personal advice: go for an 8x8 matrix with low-current LEDs, it is easier on the long term. But the 4x8 variant is a nice learning experience, too, i don't want to discourage you.

Many greets and have fun!
Peter

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Thanks for your encouraging words Peter!

What are low current LEDs in your book? For me the 2mA ones, as they are sometimes labeled like that. But those are very dim and would surely lead to brightness problems in a matrix.

Regarding 8x8 matrix: that would lead to unfavorable wiring on two splitted frontpanel pcbs, right? Or would you put one 8x8 matrix on each pcb and connect only half of the matrix?

 

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No problem and thanks for the thanks :-).

There should be some 2mA "low current" LEDs out there, that are fairly visible (only low current requirements for relatively good illumination), so these would be nice in a 8x8 setup.
And then, you can probably leave half the matrix open on each individual board, to have a 4x8, that is controlled like an 8x8 from the SEQ. If you are not afraid of hacking a bit in C, it should be fairly easy to reduce the matrix from 8x8 to 8x4. Problem (i have not checked the source), i don't know if you can enable multiple matrix setups, so check that first.

As all of this is a bit complicated and as you want brightness, let me suggest something else: go for direct DOUT wiring (no matrix) on each individual board. If you only have 32 LEDs on there, this is easy with 4 DOUT shift registers, in a medium sized SMD package, these are easy to solder and won't take lots of space, it would even be possible with through-hole shift registers.

just my 2cents, you have to experiment, but in the end, that is what MIDIbox is about, learning and having fun...

Many greets,
Peter

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2 hours ago, Hawkeye said:

Problem (i have not checked the source), i don't know if you can enable multiple matrix setups, so check that first.

Looks like there are two matrices (in MBSEQ_HW.V4 files):

BLM (Optional BLM Matrix)

BLM8x8 (Additional 8x8 BLM as used for Wilba's Frontpanel)

But i don't fully understand for what they are there. What means optional/additional? Could i use them both in parallel for my own purposes (BLM > left FP and BLM8x8 > right FP)? Maybe i should ask @latigid on how his matrix layout works? He seems to have two identical pcbs too.

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Thanks @ilmenator

I'm trying to figure out how easy it is to have two 4x8 matrices instead of one 8x8. I want two identical frontpanel PCBs (8 colums/steps each).

 

standard_v4/MBSEQ_HW.V4

##################################################
# LED assignments to DOUT pins
# SR = 0: LED disabled
# SR = 1..16:  directly forwarded to DOUT pin
# SR = 17..24: forwarded to a 8x8 LED matrix
##################################################

...

##################################################
# Button assignments to DIN pins
# SR = 0: Button disabled
# SR = 1..16:  directly triggered from DIN pin
# SR = 17..24: triggered from a 8x8 button matrix
##################################################

 

If i'm correct, i can configure my own IN/OUT matrices per SR = 17..24. But i'm not sure about it.

I'd like to know what 'forwarded to a 8x8 LED matrix' or 'triggered from a 8x8 button matrix' means? Which matrices, where can i set them up?

 

 

 

Edited by tago
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  • 2 weeks later...

What serial register (select row) configuration is better?

(1) Wilba DIO layout (http://www.ucapps.de/midibox_seq/mbseq_v4_dio_wilba_layout.pdf) uses the select row SR (M1..M8) for Btns and LEDs (at the same time?).

(2) Duo LED matrix layout (http://ucapps.de/mbhp/button_duoled_matrix.pdf) has Btns and LEDs splitted with each their own select rows (DEFAULT_SRM_DOUT_CATHODES1 > D0-D3 to LEDs and > D4-D7 to Btns) I wonder why, if (1) is working as well.

 

I want to place 32 LEDs and 32 Btns on each pcb. Should i go the 8x8 route (2) or a 4x8 based on (1)? I'd think (1) with a 4x8 matrix should be the best, right?

Edited by tago
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